I live in an apt with four other people which is why the network is set up how it is. I'm currently looking into re-configuring the network so it goes cable modem -> wrt54gl -> Vonage but with the way the rooms are spaced out this might not be possible.

Other factors- I'll be the only one using the adapter (and Vonage)- Features are nice but I'm more concerned with reliability- I already have 3 routers yet for some strange reason believe you can never have enough routers

Is there a particular phone adapter I should be getting? Are there pros or cons to each specific one or are they pretty much the same?

You have to be aware that as you add router to router to router, packets will have to make round trips from router to router, which can slow down performance, so phone adapter behind 2 routers aren't a very good ideal. To get smooth transmission between you and your caller, you will have to place it behind D-Link DI-604 with D-Link VTA (be very sure you enable QoS as not to get interfered by data traffic) or Motorola VT2442 between cable modem and D-Link DI-604. You can have Motorola VT2442 between your D-Link DI-604 and WRT54GT but remember that for outgoing transmission from your phone the packets sent from your phone adapter will have to make a trip to your DI-604 before it reaches your cable modem to the Internet, so you have to be sure you give priority to the phone adapter. This is important if you have a TTY machine (teletypewriter for the deaf and hearing impaired) since TTYs are very sensitive to error.

If you wanted to go from modem to Vonage to router, then VTA rules out. However, you can plug a VTA to wrt54gl's port 1 and DI-604 to port 2. Just make sure you enable QoS for port 1.

Update:

Also, you made a right choice when you setting up networking with your Vonage phone adapter, because in office buildings, if you have 16 computers, it's always a good ideal to get a 16-port router (very expensive) instead of 5 four-port router if you setup the following:

If you have a phone adapter, you will have to have a phone adapter that lets you connect your phone adapter between your cable modem and your main router.

However in this situation, computer to router to router to phone adapter to Internet can cause a "packet delay" because of round trips between 2 routers. With a 16-port router, you will eliminate additional routers.

I really like the features of the wrt54gl and it looks like a lot of other people on this forum have it set up that way with QoS enabled. So I'll try that and see how it goes.

Lastly, does it matter which adapter I get?

Given that you think that you can never have enough routers, it comes down to cost. If the extra $40 that you'll shell out to Vonage for the VT2442 is a significant issue, then get the VTA. Otherwise get the VT2442. For what it's worth, I like my 2442. I've never had a VTA, but the traffic in here doesn't say much against it.

Yep, that's exactly the deal I'm looking at. Both are free so I figured I'd ask around to see if anyone had a preference over one or the other. I wonder why Canada is getting the VT2442 for free but the US isn't though.

Is it possible to turn DHCP off on the VT2442 so that it's my WRT54GL that's doing the routing and the VT2442 just becomes a phone adapter?

I used to be of the camp "get the most you can if it's free", but that isn't always the best for all situations. And I don't believe it applies to Voip adapters.

I have my own router (wrt54g) running 3rd party firmware. I also have an HBB1 that does an amazing job of QoS. I don't need another router on my network. Reading through the forum topics, it's suggested that the Voip adapters which do not have router functionality are more stable overall since there is far less in firmware that can go wrong and less the developers of the firmware have to worry about. I recently switched from an RTP300 to a D-Link VTA-VR. The RTP300 was dying a slow death (the latest firmware botch by Vonage forced my hand). The VTA-VR, to me, has better sound quality and has been very stable in the 3 or so weeks I've had it in service.

If you already have a router, and don't need another one, why make the Voip adapter do something that it doesn't need to.